Energy sources useful for the generation of electricity include wind, water, solar, nuclear and steam energy and various methods and systems have been developed for harnessing such energy to generate electricity, typically by performing useful work to drive an electric generator.
With the continuing need for energy consumption efficiency and conservation, many efforts have been made to exploit previously unused energy sources. Many methods and systems have been proposed for the harnessing of existing forces or mechanical work to generate electrical power. In particular, several systems and methods have been developed to use the energy and downward force of the wheels of vehicles as they move along a roadway surface.
The systems can be categorized generally as mechanical systems, air compression systems and hydraulic systems.
Mechanical Systems.
Mechanical systems for generating electric power from the downward force of vehicles passing over a roadway typically involve gear mechanisms and other moving parts and are prone to wear and tear from the stress of forced downward movement in response to vehicles and forced upward movement when being reset. One example is U.S. Pat. No. 4,238,687 to Martinez discloses a system for generating electric power from the passage of motor vehicles over a roadway using turbines that are driven by the downward rotational movement of arc-shaped arms connected to rocker plates installed on a road surface when such rocker plates are forced down by vehicles passing over them.
Air Compression Systems.
Air compression systems typically involve an air compression piston being driven by an actuator of some sort that translates the downward force of a vehicle passing over a roadway in which the actuator is installed. For example, U.S. Pat. No. 4,173,431 to Smith discloses a road vehicle-actuated air compressor and system for using compressed air to operate an electrical generator to generate electricity. The road vehicle-actuated compressor includes an actuator that is pushed downward by the weight of vehicle tires passing over it, driving a reciprocating piston in a cylinder, compressing the air in the cylinder. An electric generator is driven by compressed air from the cylinder. Another example is U.S. Pat. No. 5,634,774 to Angel et al. which discloses a road vehicle actuated air compressor which utilizes flaps mounted in pairs in a road or pedestrian walkway surface. When traffic moves over the flaps, the flaps move downward to activate a piston which compresses air. The compressed air is stored and used as needed to generate electricity. Air compression systems, while generally somewhat more durable than mechanical systems, are not efficient in maximizing the amount of energy translated from the downward forces of moving vehicles to drive an electrical generator, due to friction and other losses.
Hydraulic Systems.
Several systems utilize hydraulic pumps to absorb the downward force of vehicles passing over a roadway and translate same into useful work, such as to drive an electric generator. For example, U.S. Pat. No. 4,004,422 to Le Van discloses a method and apparatus for producing useful work utilizing the weight of moving traffic by incorporating in a roadway or traffic-way a readily deformable chamber which is filled with a fluid, arranged so that the weight of the vehicle is passing over it causes displacement of the fluid contained therein. The energy of the displaced fluid in turn is translated into mechanical or electric energy. U.S. Pat. No. 4,130,064 to Bridwell discloses a system for utilizing the weight and momentum of moving vehicles to produce usable energy comprising a fluid displacement pump positioned either under a moveable plate in a roadway or between the rail in a railbed in a railway which compresses hydraulic fluid as the vehicle passes over, a low pressure line for supplying fluid to the pump chamber, a high pressure outlet line communicating with the chamber and connected to a manifold which is supplied with high pressure fluid from a number of other similar pumps and which directs the fluid to an energy conversion device such as a fluid motor and electric generator. The invention teaches use of a dual-stroke pump actuated depending on the weight of the passing vehicles. The dual-stroke pump allows greater volumes of hydraulic fluid to be pressurized depending on the weight of the passing vehicle.
Similarly, U.S. Pat. No. 4,211,078 to Bass is directed to a power source comprising a cylinder arranged to pump hydraulic fluid into a pressure accumulator. The stored hydraulic fluid operates a hydraulic motor to drive an alternator to generate electric power. The cylinder can be a single acting cylinder having a piston rod depressed by the weight of passing traffic on a highway. The system uses an accumulator and a hydraulic motor which drives an alternator to generate electric power. U.S. Pat. No. 4,409,489 to Hayes discloses an apparatus which pressurizes fluid and causes it to flow by capturing energy dissipated by moving vehicles, comprising a network of collapsible bodies containing hydraulic fluid attached to a turbine generator system. The collapsible bodies are resilient tubes, preferably three-part structures made of elastic inner tubes with projections and outer sections of semi-rigid hose. The claimed improvement is in the use of a network of numerous collapsible bodies to capture more weight from passing vehicles.
More recent efforts include U.S. Pat. No. 6,172,426 to Galich discloses an energy platform system for generating electrical energy from the weight of a moving vehicle comprising a fluid bed containing a volume of fluid which is compressible by the weight of a moving vehicle driven over it. Fluid forced from within the bladder as a result of such compression passes through a circulation system where the moving fluid is used to drive a generator. The circulation assembly comprises an accumulator in fluid communication with the bladder, which receives the forced fluid and releases it at a specified pressure level. A hydraulic pump and reservoir are also used. The electrical generator is a linear generator, comprising an elongate cylinder having a hollow interior. The exterior of the cylinder has a coil around it. A rod is inserted within the cylinder and has a magnet slidably coupled to it. As the rod in the cylinder is moved by the hydraulic fluid, the magnet moves as well, causing an electrical current within the coil. U.S. Pat. No. 6,204,568 to Runner discloses a system for converting mechanical motion of vehicles into electrical energy, comprising a plurality of motion converter assemblies each including a rod which remains in communication with a vertical motion delivery mechanism through a gearing mechanism for rotating the rod in response to vehicle traffic passing over the system, a plurality of fluid pumps each connected to the rotating rod to generate pressurized fluid which in turn drives a turbine generator. The motion converter assemblies have a rectangular base and sides forming a box an are inserted in the road surface. The motion converter assemblies also have a pair of rectangular top plates that are pivotally connected at one end to one side of the motion connection assembly base, with springs urging the plates upward. The top plate has a vertical plate pivotally connected to its under side which has teeth to engage a gear. When a vehicle passes over the top plate of a motion converter assembly, the vertical plate is driven downward and engages the gear, which rotates and drives the fluid pumps.
These previously described systems, while in principle capable generating electrical power from the downward force of vehicles as they pass over a roadway, are inefficient in their ability to maximize the electrical power generated from each passing vehicle. Vehicles have varying weights; the downward force of a semi-truck is obviously considerably more than that of a compact car. Prior systems do not effectively harness the full force of each vehicle. Additionally, because vehicle traffic is typically irregular, there is an increased need in such a system to maximize the transfer of energy from each vehicle and store energy to provide a steady supply of electric power. An embodiment of the present invention is a system and method for generating power, such as electrical power, from downward vehicle forces on a roadway that effectively harnesses the energy of vehicles of varying weights. Embodiments of the present invention may overcome the shortcomings of prior efforts by employing multiple hydraulic cylinders of different load bearing and hydraulic fluid compression capacities that are selectively activated by a sensor system depending on vehicle weight in a novel combination and configuration with a road plate over which vehicles pass. Embodiments of the present invention can effectively harness the downward force of both moving and stationary vehicles.